Prostatic carcinoma is one of the most common carcinomas in man. Because of the large number of surgical procedures for this disease at our university hospital and at its associated Veterans Administration hospital, this tumor is abundantly available in our center. The task of discovering the fundamental differences between normal and malignant prostatic epithelial cells is complicated by the fact that malignant prostatic tumors contain large numbers of fibroblasts, endothelial cells, lymphocytes, and blood cells in addition to the malignant cells. Similarly, the normal precursor of the malignant prostatic epithelial cell represents a minority of the cells found in normal prostates. Using methods which we have used previously fo the disaggregation of tissues and for the purification of single kinds of cells from tissues, we shall develop methods for the purification of normal and malignant prostatic epithelial cells. In preliminary work in both the hamster and man, we have used gradient sedimentation for the purification of normal viable prostatic epithelial cells; however, we currenty obtain a low yield (cells/gram of tissue) of cells from the human prostate using pronase and believe that other agents for the disaggregation of the human prostate need to be studied. We have worked with only one prostatic carcinoma. After determining the optimal conditions for the disaggregation of tissues and for the purification of normal and malignant prostatic epithelial cells, we shall determine the best conditions for freezing and storing them over liquid nitrogen. The purified epithelial cells will be tested in several tissue culture systems in order to determine conditions which will permit their growth. The absence of fibroblasts in the purified inoculum for culture will prevent overgrowth of the cultures by fibroblasts. The purified cells will be tested for tumorgenicity by heterologous transplantatton.